JP2009260287A - Novel organic semiconductor material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low molecule organic semiconductor material excellent in solubility consisting of thiophene and phenylene, which can be manufactured by simple processes such as coating and printing. <P>SOLUTION: The organic semiconductor material is represented by general formula (I). In the general formula (I), R<SP>1</SP>, R<SP>2</SP>, R<SP>3</SP>, R<SP>4</SP>, R<SP>5</SP>and R<SP>6</SP>are each independently a substituted or non-substituted alkyl group, a substituted or non-substituted alkoxy group, or a substituted or non-substituted alkylthio group or hydrogen, at least one of R<SP>2</SP>, R<SP>3</SP>, R<SP>5</SP>and R<SP>6</SP>is a substituted or non-substituted alkyl group, a substituted or non-substituted alkoxy group, or a substituted or non-substituted alkylthio group, and n is an integer of 1 to 8. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a novel organic semiconductor material, and the obtained organic semiconductor material is extremely useful as an organic electronics material.

  In recent years, research and development of organic thin film transistors using organic semiconductor materials has been active. Organic semiconductor materials can be formed into thin films by a simple process using a wet process such as a printing method, spin coating method, etc., and have the advantage that the manufacturing process temperature can be lowered compared to conventional thin film transistors using inorganic semiconductor materials. There is. This enables formation on plastic substrates with generally low heat resistance, which can reduce the weight and cost of electronic devices such as displays, and is expected to be used in a variety of ways, including applications that take advantage of the flexibility of plastic substrates. it can.

  So far, poly (3-alkylthiophene) (Non-Patent Document 1), a copolymer of dialkylfluorene and bithiophene (Non-Patent Document 2), and the like have been proposed as organic semiconductor materials. Since these organic semiconductor materials have low solubility, they can be thinned by coating or printing without going through a vacuum deposition process. However, these polymer materials are limited by the purification method, and it is very troublesome to obtain a high-purity material, and the problem is that the quality is not stable due to the presence of molecular weight and molecular weight distribution. It has become.

  On the other hand, acene-based materials such as pentacene have been reported as low-molecular organic semiconductor materials (for example, Patent Document 1). Although organic thin film transistors using pentacene as an organic semiconductor layer have been reported to have a relatively high mobility, these acene-based materials have extremely low solubility in general-purpose solvents, and they are used in organic thin film transistors. When thinning the semiconductor layer, it is necessary to go through a vacuum deposition process. Therefore, it does not meet the expectation for an organic semiconductor material that a thin film can be formed by a simple process such as coating and printing as described above.

  As other low molecular organic semiconductor materials, low molecular materials composed of thiophene and phenylene have been proposed. Non-Patent Document 3 shows materials in which alkyl groups are introduced at both ends of a low-molecular material composed of thiophene and phenylene, and these materials exhibit relatively high mobility. However, as a result of investigations by the present inventors, it has been found that the solubility in general-purpose solvents at room temperature is not satisfactory. Improving solubility is important not only from the perspective of the process selection in device fabrication, but also from the viewpoint of the purification process in the production of organic semiconductor materials, and further material development is desired. .

  In order to solve the above-mentioned problems, an object of the present invention is to provide a low-molecular organic semiconductor material excellent in solubility composed of thiophene and phenylene, which can be produced by a simple process such as coating or printing.

As a result of intensive studies to achieve the above object, the present inventors have found that the above problems can be solved by introducing a modifying group at a specific site, and have completed the present invention.
That is, the present invention is solved by the following (1) to (10).
(1) "Organic semiconductor material characterized by being represented by the following general formula (I);

（一般式（Ｉ）中、Ｒ^１、Ｒ^２、Ｒ^３、Ｒ^４、Ｒ^５及びＲ^６は、それぞれ独立に、置換もしくは無置換のアルキル基、置換もしくは無置換のアルコキシ基又は置換もしくは無置換のアルキルチオ基又は水素を表わし、Ｒ^２、Ｒ^３、Ｒ^５及びＲ^６の少なくとも一つは、置換もしくは無置換のアルキル基、置換もしくは無置換のアルコキシ基又は置換もしくは無置換のアルキルチオ基であり、ｎは１〜８の整数を表わす。）」；
（２） 「前記一般式（Ｉ）において、Ｒ^２及びＲ^３が同一であることを特徴とする前記第（１）項に記載の有機半導体材料」；
（３） 「前記一般式（Ｉ）において、Ｒ^２及びＲ^３が同一であり、かつ、Ｒ^５及びＲ^６が同一であることを特徴とする前記第（１）項又は第（２）項に記載の有機半導体材料」；
（４） 「前記一般式（Ｉ）において、Ｒ^２、Ｒ^３、Ｒ^５及びＲ^６が同一であり、かつ、メチル基、メトキシ基又はメチルチオ基のうちの一つから選択されるものであることを特徴とする前記第（１）項乃至第（３）項に記載の有機半導体材料」；
（５） 「前記第（１）項乃至第（４）項のいずれかに記載の有機半導体材料からなることを特徴とする電荷輸送性部材」；
（６） 「有機半導体層を具備する有機薄膜トランジスタであって、前記有機半導体層が、前記第（５）項に記載の電荷輸送性部材からなることを特徴とする有機薄膜トランジスタ」；
（７） 「有機半導体層を介して互いに分離した対の第１の電極と第２の電極と、電圧を印加することにより、前記第１の電極と前記第２の電極との間の有機半導体層内を流れる電流をコントロールする機能を具備する第３の電極を具備していることを特徴とする前記第（６）項に記載の有機薄膜トランジスタ」；
（８） 「前記第３の電極と、前記有機半導体層との間に、絶縁膜が設けられていることを特徴とする前記第（７）項に記載の有機薄膜トランジスタ」；
（９） 「前記第（６）項乃至第（８）項のいずれか一項に記載の有機薄膜トランジスタにより表示画素が駆動されることを特徴とするディスプレイ装置」；
（１０） 「前記表示画素は、液晶素子、エレクトロルミネッセンス素子、エレクトロクロミック素子、及び電気泳動素子の中から選ばれたものであることを特徴とする前記第（９）項に記載のディスプレイ装置」。

(In general formula (I), R ¹ , R ² , R ³ , R ⁴ , R ⁵ and R ⁶ are each independently a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, or a substituted or unsubstituted group. Represents a substituted alkylthio group or hydrogen, and at least one of R ² , R ³ , R ⁵ and R ⁶ is a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group or a substituted or unsubstituted alkylthio group; And n represents an integer of 1 to 8) ";
(2) “The organic semiconductor material according to (1), wherein R ² and R ³ are the same in the general formula (I)”;
(3) The item (1) or the item (2), wherein, in the general formula (I), R ² and R ³ are the same, and R ⁵ and R ⁶ are the same. Organic semiconductor material described in “
(4) “In the general formula (I), R ² , R ³ , R ⁵ and R ⁶ are the same and are selected from one of a methyl group, a methoxy group and a methylthio group. The organic semiconductor material according to any one of (1) to (3) above,
(5) “A charge transporting member comprising the organic semiconductor material according to any one of (1) to (4)”;
(6) "Organic thin film transistor comprising an organic semiconductor layer, wherein the organic semiconductor layer comprises the charge transporting member according to item (5)";
(7) “Organic semiconductor between the first electrode and the second electrode by applying a voltage to a pair of the first electrode and the second electrode separated from each other via the organic semiconductor layer An organic thin film transistor according to item (6), further comprising a third electrode having a function of controlling a current flowing in the layer;
(8) “The organic thin film transistor according to item (7), wherein an insulating film is provided between the third electrode and the organic semiconductor layer”;
(9) “Display device in which a display pixel is driven by the organic thin film transistor according to any one of (6) to (8)”;
(10) The display device according to (9), wherein the display pixel is selected from a liquid crystal element, an electroluminescence element, an electrochromic element, and an electrophoretic element. .

  According to the present invention, a low molecular organic semiconductor material composed of thiophene and phenylene having excellent solubility, which can be manufactured by a simple process such as coating or printing, can be provided.

The schematic block diagram of an example of an organic thin-film transistor is shown. It is a DSC chart of the compound synthesize | combined in Example 1 in this invention. It is a DSC chart of the compound synthesize | combined in Example 2 in this invention. It is a DSC chart of the compound synthesize | combined in Example 3 in this invention. It is a DSC chart of the compound synthesize | combined in Example 4 in this invention. 10 is a graph showing output characteristics of a transistor manufactured in Example 5. FIG.

Hereinafter, the present invention will be described in detail.
First, the structure of the organic semiconductor material of the present invention will be described. The structure of the organic semiconductor material of the present invention is represented by the following general formula (I).

In general formula (I), R ¹ , R ² , R ³ , R ⁴ , R ⁵ and R ⁶ are each independently a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, or a substituted or unsubstituted group. Represents an alkylthio group or hydrogen.

Specific examples of the alkyl group represented by R ¹ include methyl group, ethyl group, n-propyl group, i-propyl group, t-butyl group, s-butyl group, n-butyl group, and i-butyl group. Pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, 3,7-dimethyloctyl group, 2-ethylhexyl group, trifluoromethyl group, 2-cyanoethyl group, benzyl group , 4-chlorobenzyl group, 4-methylbenzyl group, cyclopentyl group, cyclohexyl group and the like can be mentioned as examples. As an alkoxy group and an alkylthio group, an oxygen atom or a sulfur atom is inserted at the bonding position of the alkyl group. An alkoxy group or an alkylthio group is an example. As mentioned in the above example, a branched chain may be introduced, but since it may adversely affect the packing of crystals, the introduction of a straight chain is more preferable.

It has been clarified that the organic semiconductor material of the present invention drastically improves the solubility in a solvent by having substituents represented by R ² , R ³ , R ⁵ and R ⁶ .
Examples of the alkyl group represented by R ² , R ³ , R ⁵ and R ⁶ are the same as those of R ¹ described above, specifically, methyl group, ethyl group, n-propyl group, i- Propyl group, t-butyl group, s-butyl group, n-butyl group, i-butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, 3,7 Examples include -dimethyloctyl group, 2-ethylhexyl group, trifluoromethyl group, 2-cyanoethyl group, benzyl group, 4-chlorobenzyl group, 4-methylbenzyl group, cyclopentyl group, cyclohexyl group and the like. Examples of the group and the alkylthio group include those in which an oxygen atom or a sulfur atom is inserted into the bonding position of the alkyl group to form an alkoxy group or an alkylthio group. Can be mentioned.

Further, the effect of imparting solubility due to the presence of R ² , R ³ , R ⁵ or R ⁶ is very large, and the solubility is dramatically improved even if only the smallest methyl group is introduced as an alkyl group. This solubility-imparting effect is an effect caused by inhibiting the interaction between C—H located in the lateral direction of the benzene ring and the π electron of the adjacent molecule, and the same effect can be obtained for an alkoxy group or an alkylthio group. can get. However, when R ² , R ³ , R ^5, or R ⁶ becomes sterically large, the distance between adjacent molecules in the crystal is increased, and charge transport properties are degraded. Therefore, R ² , R ³ , R ⁵ or R ⁶ is preferably an alkyl group, an alkoxy group or an alkylthio group having a carbon number shorter than that of R ¹ or R ² , and specifically, an alkyl group, an alkoxy group or an alkylthio group having 2 or less carbon atoms is preferred. More preferably, it is selected from a methyl group, a methoxy group, and a methylthio group. When considering a device using this material, it is preferable that the phase transition temperature from the crystal is 120 ° C. or higher from the viewpoint of thermal stability of the device.

  It is important to improve the solubility of these materials because the manufacturing tolerance of the wet film forming process in manufacturing devices such as organic EL elements and organic transistor elements increases. For example, the choice of coating solvent is expanded, the temperature range during solution preparation is expanded, the temperature and pressure range during solvent drying is expanded, and the high processability results in high purity and high uniformity. The possibility of obtaining a high-quality thin film increases.

In the general formula (I), the thiophene repeat number n represents an integer of 1 to 8. Although the solubility is improved by having a substituent in R ² and / or R ³ , the solubility decreases as the number of thiophene rings increases and insolubilization occurs, and the ionization potential becomes shallower. Further repetition of the thiophene ring is not preferred because it becomes unstable in the atmosphere.

Next, the manufacturing method of the oligomer of this invention is demonstrated.
The method for synthesizing the organic semiconductor material of the present invention is not particularly limited, and it can be synthesized by various known methods. As an example, Suzuki coupling (hereinafter referred to as Suzuki coupling) of a halide and a boronic acid compound,

  Alternatively, Stille coupling of a halide and a tin compound,

  Alternatively, Kumada coupling (Kumada coupling) of halide and Grignard reagent,

  Alternatively, oxidative coupling using an oxidizing agent such as copper chloride

  Or Yamamoto reaction between halides

等をはじめとする、公知のアリール基間の種々のカップリング反応により、或いはこれら反応を組み合わせて段階的に合成することにより、非対称分子においても容易に製造することができる。

Asymmetric molecules can also be easily produced by various coupling reactions between known aryl groups, including the above, or by stepwise synthesis by combining these reactions.

As an example, a method using Suzuki coupling will be described.
The Suzuki coupling reaction is performed with a halide and a boron compound. The halogen atom of the aryl halide is preferably an iodide or bromide from the viewpoint of reactivity. As the aryl boron compound, aryl boronic acid or aryl boronic acid ester or aryl boronic acid salt is used, but the aryl boronic acid ester does not produce a trimerized anhydride (boroxine) like aryl boronic acid. Moreover, it is more preferable because of high crystallinity and easy purification. As a method for synthesizing an aryl boronic acid ester, (i) a reaction in which an aryl boronic acid and an alkyl diol are heated in an anhydrous organic solvent, and (ii) a reaction in which an alkoxy boron ester is added after metalation of the halogen moiety of the aryl halide. (Iii) Reaction of adding alkoxyboron ester after preparing Grignard reagent of aryl halogen, and (iv) Heating aryl halide and bis (pinacolato) diboron or bis (neopentylglycolato) diboron under palladium catalyst It is obtained by reacting.

Examples of the palladium catalyst used include various catalysts such as Pd (PPh ₃ ) ₄ , PdCl ₂ (PPh ₃ ) ₂ , Pd (OAc) ₂ , PdCl ₂ , or palladium carbon to which triphenylphosphine is additionally added as a ligand. Can be used. Of these, Pd (PPh ₃ ) ₄ is used most generally.

A base is always required in the Suzuki coupling reaction, but relatively weak bases such as Na ₂ CO ₃ , NaHCO ₃ , K ₂ CO ₃ give good results. When affected by steric hindrance or the like, strong bases such as Ba (OH) ₂ and K ₃ PO ₄ are effective, and caustic soda is also effective depending on the reaction substrate. Other caustic potash, metal alkoxides, etc., such as potassium t-butoxide, sodium t-butoxide, lithium t-butoxide, potassium 2-methyl-2-butoxide, sodium 2-methyl-2-butoxide, sodium methoxide, sodium ethoxide, potassium Ethoxide, potassium methoxide and the like can also be used.

Further, a phase transfer catalyst may be used to make the reaction proceed more smoothly, preferably tetraalkylammonium halide, tetraalkylammonium hydrogensulfate, or tetraalkylammonium hydroxide. -N-butylammonium halide, benzyltriethylammonium halide, or tricaprylylmethylammonium chloride.
Although the atmosphere of the reaction can be performed in the air, it is preferable to perform the reaction in an inert gas atmosphere such as nitrogen or argon because the catalyst used may be deteriorated.

  Examples of the reaction solvent include alcohols such as methanol, ethanol, isopropanol, butanol, 2-methoxyethanol, 1,2-dimethoxyethane, and bis (2-methoxyethyl) ether, and ether ethers, and cyclic ethers such as dioxane and tetrahydrofuran. Benzene, toluene, xylene, dimethyl sulfoxide, N, N-dimethylformamide, N-methylpyrrolidone, 1,3-dimethyl-2-imidazolidinone and the like. The solvent is preferably used after deaeration.

  The organic semiconductor material obtained as described above is used after removing impurities such as catalysts, inorganic salts, unreacted raw materials, and by-products used in the reaction. For the purification operation, conventionally known methods such as recrystallization, various chromatographic methods, sublimation purification, reprecipitation, extraction, Soxhlet extraction, ultrafiltration, dialysis and the like can be used. Since contamination with impurities adversely affects the semiconductor characteristics, it is desirable to make the purity as high as possible. The material of the present invention having excellent solubility has less restrictions on these purification methods, and as a result, has a positive effect on semiconductor characteristics.

  The semiconductor material of the present invention obtained by the above production method can be formed into a thin film by dissolving it in a solvent such as dichloromethane, tetrahydrofuran, chloroform, toluene, dichlorobenzene, and xylene and applying the solution on a support. For example, a thin film can be formed by a known wet film formation method such as a spin coating method, a casting method, a dipping method, an ink jet method, a doctor blade method, a screen printing method, a dispensing method, or the like. Further, depending on the casting method or the like, it is possible to take a form of a flat crystal or a thick film state. These thin films, thick films, or crystals function as charge transporting members for various functional elements such as photoelectric conversion elements, thin film transistors, and light emitting elements.

  Depending on the device to be produced, an appropriate combination is selected from the above-described film forming methods or solvents. Of course, the film can also be formed by a dry process such as a vacuum deposition method.

  Next, the organic thin film transistor of the present invention will be described with reference to a schematic structural diagram in FIG.

The organic semiconductor layer (1) constituting the organic thin film transistor is mainly composed of the compound represented by the general formula (I) of the present invention.
The organic thin film transistor has a first electrode (source electrode): (2) and a second electrode (drain electrode): (3) separated and formed via an organic semiconductor layer (1). Opposing third electrode (gate electrode): (4).

An insulating film (5) may be provided between the gate electrode (4) and the organic semiconductor layer (1).
In the organic thin film transistor, a current flowing in the organic semiconductor layer (1) between the source electrode (2) and the drain electrode (3) is controlled by applying a voltage to the gate electrode (4).

The organic thin film transistor of the present invention is formed on a predetermined support.
A conventionally known substrate material can be applied as the support, and examples thereof include glass, silicon, and plastic. By using a conductive substrate, the gate electrode (4) can also be used.

  In addition, the gate electrode (4) and the conductive substrate may be laminated, but when the organic thin film transistor of the present invention is applied to a device, practical aspects such as flexibility, weight reduction, low cost, impact resistance, etc. In order to improve the characteristics, it is preferable to use a plastic sheet as the support.

  Examples of the plastic sheet include polyethylene terephthalate, polyethylene naphthalate, polyethersulfone, polyetherimide, polyetheretherketone, polyphenylene sulfide, polyarylate, polyimide, polycarbonate, cellulose triacetate, and cellulose acetate propionate. It is done.

Next, components other than the organic semiconductor layer in the organic thin film transistor of FIG. 1 will be described.
The organic semiconductor layer (1) is formed in contact with the first electrode (source electrode), the second electrode (drain electrode), and, if necessary, the insulating film 5.

The insulating film (5) will be described.
The insulating film constituting the organic thin film transistor is formed using various insulating film materials. For example, silicon oxide, silicon nitride, aluminum oxide, aluminum nitride, titanium oxide, tantalum oxide, tin oxide, vanadium oxide, barium strontium titanate, zirconium barium titanate, lead zirconate titanate, lead lanthanum titanate, titanate Examples thereof include inorganic insulating materials such as strontium, barium titanate, barium magnesium fluoride, bismuth tantalate niobate, and yttrium trioxide.

  Also, for example, polymer compounds such as polyimide, polyvinyl alcohol, polyvinylphenol, polyester, polyethylene, polyphenylene sulfide, polystyrene, polymethacrylic acid ester, unsubstituted or halogen atom-substituted polyparaxylylene, polyacrylonitrile, cyanoethyl pullulan, etc. may be used. Can do.

  Furthermore, two or more of the above insulating materials may be used in combination. Among these, materials are not particularly limited, but those having a high dielectric constant and a low electrical conductivity are preferable.

  As a method for forming the insulating film 5, for example, a dry process such as a CVD method, a plasma CVD method, a plasma polymerization method, a vapor deposition method, a spray coating method, a spin coating method, a dip coating method, an ink jet method, a casting method, a blade coating method. And a wet process by coating such as a bar coating method.

  Next, interface modification between the organic semiconductor layer 1 and the insulating film (5) will be described.

The organic thin film transistor is insulated from the organic semiconductor layer (1) for the purpose of improving the adhesion between the insulating film (5) and the organic semiconductor layer (1) and reducing the driving voltage and the leakage current. A predetermined organic thin film may be provided between the film (5).
The organic thin film is not particularly limited as long as it does not chemically affect the organic semiconductor layer. For example, an organic molecular film or a polymer thin film can be used.
Examples of the organic molecular film include coupling agents such as octadecyltrichlorosilane and hexamethyldisilazane.

As the polymer thin film, the above-described polymer insulating film materials can be used, and these may function as a kind of insulating film.
The organic thin film may be subjected to an anisotropic treatment by rubbing or the like.

  Next, the electrode which comprises an organic thin-film transistor is demonstrated.

  The organic thin film transistor of the present invention includes a pair of a first electrode (source electrode) and a second electrode (drain electrode) separated from each other via an organic semiconductor layer, and a voltage applied to the first thin film transistor. A third electrode (gate electrode) having a function of controlling a current flowing in the organic semiconductor layer between the second electrode and the second electrode is provided. Since the organic thin film transistor is a switching element, the amount of current flowing between the first electrode (source electrode) and the second electrode (drain electrode) can be greatly modulated by the voltage application state of the third electrode (gate electrode). is important. This means that a large current flows when the transistor is driven, and no current flows when the transistor is not driven.

  The gate electrode and the source electrode are not particularly limited as long as they are conductive materials. For example, platinum, gold, silver, nickel, chromium, copper, iron, tin, antimony, lead, tantalum, indium, aluminum, Zinc, magnesium, etc., and alloys thereof, conductive metal oxides such as indium / tin oxide, or inorganic and organic semiconductors whose conductivity has been improved by doping, such as silicon single crystal, polysilicon, amorphous silicon, Germanium, graphite, polyacetylene, polyparaphenylene, polythiophene, polypyrrole, polyaniline, polythienylene vinylene, polyparaphenylene vinylene, a complex of polyethylene dioxythiophene and polystyrene sulfonic acid, and the like can be applied.

  It is desirable that the source electrode and the drain electrode have a small electric resistance at the contact surface with the semiconductor layer.

  As a method for forming the electrode, for example, by applying a known photolithography method or a lift-off method to a conductive thin film formed by using a method such as vapor deposition or sputtering using the electrode forming material as a raw material, The method of making it into a shape is mentioned.

  Further, a method of etching on a metal foil such as aluminum or copper by using a resist by thermal transfer, ink jet, or the like can be applied.

  Alternatively, a conductive polymer solution or dispersion, or a conductive fine particle dispersion may be directly patterned by inkjet, or may be formed from the coating film by lithography, laser ablation, or the like.

  Furthermore, a method of patterning an ink containing a conductive polymer or conductive fine particles, a conductive paste, or the like by a printing method such as relief printing, intaglio printing, planographic printing, or screen printing can also be applied.

The organic thin film transistor of the present invention may be provided with an extraction electrode from each electrode as necessary.

  In addition, the organic transistor of the present invention is stably driven even in the atmosphere, but it is necessary for protection from mechanical destruction, protection from moisture and gas, or protection for the convenience of device integration. A protective layer can also be provided.

  The organic thin film transistor of the present invention described above can be suitably used as an element for driving various conventionally known display image elements such as liquid crystal, electroluminescence, electrochromic, electrophoresis, and so on. It is possible to produce a display called “paper”.

  The display device of the present invention includes, for example, a liquid crystal display element in a liquid crystal display device, an organic or inorganic electroluminescence display element in an EL display device, and a display element such as an electrophoretic display element in an electrophoretic display device as one display pixel. A plurality of display elements are arranged in a matrix in the X and Y directions. The display element includes the organic thin film transistor of the present invention as a switching element for applying voltage or supplying current to the display element. The display device of the present invention includes a plurality of the switching elements corresponding to the number of the display elements, that is, the number of display pixels.

  The display element includes, in addition to the switching element, for example, a substrate, an electrode such as a transparent electrode, a polarizing plate, a color filter, and the like. However, these components are not particularly limited and may be used depending on the purpose. Can be appropriately selected, and conventionally known ones can be used.

  When the display device forms a predetermined image, for example, the switching element arbitrarily selected from the switching elements arranged in a matrix form applies voltage or current to the corresponding display element. By configuring the switch to be turned on or off only when supplying, and to be turned off or on at other times, display of the display device can be performed at high speed and high contrast. As an image display operation in the display device, an image or the like is displayed by a conventionally known display operation. For example, in the case of the liquid crystal display element, an image or the like is displayed by controlling the molecular arrangement of the liquid crystal by applying a voltage to the liquid crystal. In the case of the organic or inorganic electroluminescence display element, an image or the like is displayed by supplying a current to a light emitting diode formed of an organic or inorganic film to cause the organic or inorganic film to emit light. In the case of the electrophoretic display element, for example, a voltage is applied to white and black colored particles charged to different polarities, and the particles are electrophoresed between electrodes in a predetermined direction to generate an image or the like. Is displayed.

  The display device can be manufactured by a simple process such as coating and printing of the switching element, and can use a substrate that cannot withstand high-temperature processing such as a plastic substrate or paper, and can be a large-area display. However, the switching element can be fabricated with energy saving and low cost.

  Further, an IC in which the organic thin film transistor of the present invention is integrated can be used as a device such as an IC tag.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by these examples unless it exceeds the gist.

  The (thiol-1) thiophene compound was synthesized by the following synthesis route.

  To a 100 ml flask, 1.823 g (41.78 mmol) of sodium hydride (55% in oil) was added and purged with argon, and then 20 ml of DMF was added. To this solution, 8.000 g (39.79 mmol) of 4-bromo-2,6-dimethylphenol was added little by little, and after stirring at room temperature for 30 minutes, bromohexane was added and further stirred at 60 ° C. for 3 hours. It returned to room temperature and water and hexane were added. The organic layer was washed with water and saturated brine in that order, and dried over anhydrous sodium sulfate. After the desiccant was filtered off, the solvent was distilled off under reduced pressure. The residue was purified by column chromatography (ethyl acetate / hexane = 5/95) to obtain 11.23 g (39.37 mmol) of 1-bromo-4-hexyloxy-2,6-dimethylbenzene as a colorless liquid. Yield 98%.

  In a 300 ml flask, 9.000 g (31.55 mmol) of 1-bromo-4-hexyloxy-2,6-dimethylbenzene was placed and purged with argon, and then 160 ml of THF was added. After cooling to -74 ° C, 20.1 ml of a 1.65 M hexane solution of n-butyllithium was added dropwise. After completion of dropping, the mixture was stirred for 30 minutes, 7.045 g (37.86 mmol) of 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane was added, and the mixture was further stirred for 30 minutes. After returning to room temperature and adding an aqueous ammonium chloride solution and hexane, the organic layer was washed with water and saturated brine in that order, and dried over anhydrous sodium sulfate. After the desiccant was filtered off, the solvent was distilled off under reduced pressure. The residue was purified by column chromatography (ethyl acetate / hexane = 5/95) to give 2- (4-hexyloxy-3,5-dimethylphenyl) -4,4,5,5-tetramethyl- as a colorless liquid. As a result, 7.95 g (23.92 mmol) of 1,3,2-dioxaborolane was obtained. Yield 76%.

  In a 50 ml flask was added 1.500 g (4.514 mmol), 5,5 ′ 2- (4-hexyloxy-3,5-dimethylphenyl) -4,4,5,5-tetramethyl-1,3,2-dioxaborolane. -Dibromo-2,2'-bithiophene 0.714g (2.202mmol) and tetrakis (triphenylphosphine) palladium 127.2mg (0.110mmol) were added, and argon substitution was carried out. 13 ml of degassed toluene, 12 ml of degassed 2M aqueous sodium carbonate solution and 1 drop of trioctylmethylammonium chloride were added and stirred at 95 ° C. for 7.5 hours. After returning to room temperature and diluting with toluene, the solution was washed with water and saturated brine in this order. After passing through a short column of silica gel (toluene), recrystallization from ethyl acetate yielded 1.061 g (1.846 mmol) of (Real-1) thiophene compound. Yield 84%.

IR (KBr) ν / cm ⁻¹ : 3066, 2946, 2928, 2880, 2866, 2841, 1736, 1585, 1464, 1445, 1378, 1264, 1227, 1167, 1146, 1070, 1043, 988, 924, 867, 796, 769, 491.
FIG. 2 shows the result of DSC measurement of the thiophene compound of (Real 1).

The solubility of (Real-1) thiophene compound in various solvents at room temperature was evaluated.
It was easily soluble in toluene, THF, chlorobenzene, dichlorobenzene, chloroform and dichloromethane, soluble in ethyl acetate and hexane, and hardly soluble in ethanol and methanol.

  Synthesis of (Real-2) Thiophene Compound

  In a 50 ml flask was added 1.500 g (3.602 mmol), 5,5 ′ 2- (4-dodecyloxy-3,5-dimethylphenyl) -4,4,5,5-tetramethyl-1,3,2-dioxaborolane. -Dibromo-2,2′-bithiophene 0.531 g (1.637 mmol) and tetrakis (triphenylphosphine) palladium 94.6 mg (0.082 mmol) were added, and the atmosphere was replaced with argon. 12 ml of degassed toluene, 9.6 ml of degassed 2M sodium carbonate aqueous solution and 1 drop of trioctylmethylammonium chloride were added and stirred at 95 ° C. for 7.5 hours. After returning to room temperature and diluting with toluene, the solution was washed with water and saturated brine in this order. After passing through a short column of silica gel (toluene / hexane = 1/1), 0.962 g (1.294 mmol) of (real-2) was obtained by recrystallization from a mixed solvent of toluene / ethanol. Yield 79%.

IR (KBr) (nu) / cm < ^-1 >: 2955,2921,2851,1728,1587,1468,1447,1378,1267,1230,1167,1078,1043,997,954,866,795,789,721,493.
FIG. 3 shows the result of DSC measurement of the thiophene compound of (Real-2).

The solubility in (solvent-2) of various solvents at room temperature was evaluated.
It was easily soluble in toluene, THF, chlorobenzene, dichlorobenzene, chloroform and dichloromethane, soluble in ethyl acetate and hexane, and hardly soluble in ethanol and methanol.

  Synthesis of (Through-3) Thiophene Compound

  In a 50 ml flask was added 1.500 g (4.514 mmol), 5,5 ′ 2- (4-hexyloxy-3,5-dimethylphenyl) -4,4,5,5-tetramethyl-1,3,2-dioxaborolane. -1.902 g (5.868 mmol) of dibromo-2,2′-bithiophene and 130 mg (0.113 mmol) of tetrakis (triphenylphosphine) palladium were added, and the atmosphere was replaced with argon. 20 ml of degassed toluene, 8 ml of degassed 2M aqueous sodium carbonate solution and 1 drop of trioctylmethylammonium chloride were added and stirred at 95 ° C. for 4.5 hours. After returning to room temperature and diluting with toluene, the solution was washed with water and saturated brine in this order. After the solvent was distilled off, the residue was purified by column chromatography to obtain 1.01 g of yellow crystals. Yield 50%.

In a 50 ml flask, 1.01 g of the crystal obtained above was put and purged with argon, and then 15 ml of THF was added. To this solution was added 0.56 ml (1.12 mmol) of a 2M THF solution of isopropylmagnesium chloride, and the mixture was stirred at room temperature for 1 hour. Then, 11.9 mg of Ni (dppe) Cl ₂ was added, and further stirred at room temperature for 2 hours. The solution was diluted with toluene, and the solution was washed with water and saturated brine in this order. After distilling off the solvent, the solution was passed through a short column of silica gel (chloroform), and then recrystallized from toluene to obtain 0.406 g (0.549 mmol) of the thiophene compound (Ex. 3). Yield 49%.
FIG. 4 shows the result of DSC measurement of the thiophene compound of (Ex. 3). It exhibits liquid crystallinity in the range of 273 to 275 ° C. during the temperature rising process and 270 to 222 ° C. during the cooling process.

The solubility of (Ex. 3) in various solvents at room temperature was evaluated.
It was easily soluble in toluene, THF, chlorobenzene, dichlorobenzene, chloroform, and dichloromethane, soluble in ethyl acetate, and hardly soluble in ethanol and methanol.

  Synthesis of (Real-4) Thiophene Compound

  2- (4-Hexyloxyphenyl) -4,4,5,5-tetramethyl-1,3,2-dioxaborolane 1.341 g (4.409 mmol), 5,5′-dibromo-2,2 in a 50 ml flask 2.00 g (6.172 mmol) of '-bithiophene and 130 mg (0.113 mmol) of tetrakis (triphenylphosphine) palladium were added to perform argon replacement. 20 ml of degassed toluene, 8 ml of degassed 2M sodium carbonate aqueous solution and 1 drop of trioctylmethylammonium chloride were added and stirred at 90 ° C. for 5 hours. After returning to room temperature and diluting with toluene, the solution was washed with water and saturated brine in this order. After the solvent was distilled off, the residue was purified by column chromatography to obtain 1.126 g of yellow crystals. Yield 61%.

  1.126 g (2.672 mmol) of yellow crystals obtained above in a 50 ml flask, 1.065 g of 2- (4-hexyloxyphenyl) -4,4,5,5-tetramethyl-1,3,2-dioxaborolane (3.206 mmol) and 77 mg (0.067 mmol) of tetrakis (triphenylphosphine) palladium were added to replace with argon. 15 ml of degassed toluene, 7 ml of degassed 2M sodium carbonate aqueous solution and 1 drop of trioctylmethylammonium chloride were added and stirred at 95 ° C. for 4 hours. After returning to room temperature and diluting with toluene, the solution was washed with water and saturated brine in this order. After the solvent was distilled off, the residue was purified by column chromatography to obtain 1.193 g of yellow crystals. Yield 82%. FIG. 5 shows the result of DSC measurement of the thiophene compound of (Ex. 4).

The solubility in (solvent 4) of various solvents at room temperature was evaluated.
It was easily soluble in toluene, THF, chlorobenzene, dichlorobenzene, chloroform, dichloromethane, and ethyl acetate, but hardly soluble in ethanol and methanol.

[Comparative Example 1]
The following thiophene compound (ratio-1) was synthesized by the same synthesis route as in Example 1 using 4-bromophenol as a starting material.

  To a 50 ml flask was added 1.000 g (3.287 mmol) of 2- (4-hexyloxy) -4,4,5,5-tetramethyl-1,3,2-dioxaborolane, 5,5′-dibromo-2,2 ′. -0.520 g (1.603 mmol) of bithiophene and 92.6 mg (0.080 mmol) of tetrakis (triphenylphosphine) palladium were added, and the atmosphere was replaced with argon. When 11 ml of degassed toluene, 9.0 ml of degassed 2M sodium carbonate aqueous solution and 1 drop of trioctylmethylammonium chloride were added and stirred at 95 ° C. for 7.5 hours, crystals of the target product were precipitated from the middle of the reaction. It was. After returning to room temperature, the precipitated crystals were collected by filtration and washed with toluene, water, ethanol, and hexane. By recrystallization from chloroform, 0.683 g (1.317 mmol) of the thiophene compound of (real-2) was obtained. Yield 82%.

The solubility in various solvents of (ratio-1) at room temperature was evaluated.
It was hardly soluble in toluene, THF, dichlorobenzene, chlorobenzene, chloroform, and dichloromethane, and insoluble in hexane, ethyl acetate, ethanol, and methanol.
[Comparative Example 2]

  The following thiophene compound (ratio-2) was synthesized by the same method as in Comparative Example 1 except that 2- (4-hexyloxy) -4,4,5,5-tetramethyl-1,3,2-dioxaborolane was used. did.

The solubility of (Ratio-2) thiophene compound in various solvents at room temperature was evaluated.
It was hardly soluble in toluene, THF, dichlorobenzene, chlorobenzene, chloroform, and dichloromethane, and insoluble in hexane, ethyl acetate, ethanol, and methanol.

[Comparative Example 3]
The solubility of the following thiophene compound (ratio-3) in various solvents at room temperature was evaluated.

It was hardly soluble or insoluble in toluene, THF, xylene, chlorobenzene, chloroform, dichloromethane, hexane, ethyl acetate, ethanol and methanol.
As described above, since the compound of this example exhibits good solubility and a high phase transition temperature, an electronic device having excellent heat resistance can be obtained using a wet process.

(Creation of thin film transistor)
A source electrode and a drain electrode were formed of gold on a p-doped silicon substrate having a thermal oxide film with a thickness of 300 nm on the surface so that the channel length was 25 μm. An organic semiconductor layer was formed by spin-coating a 1 wt% chloroform solution of the (thiol-1) thiophene compound on this substrate and drying it. When the characteristics of the thin film transistor thus manufactured were evaluated, good p-type transistor characteristics with a high on / off ratio were obtained. FIG. 6 shows output characteristics of the manufactured transistor.

1 Organic Semiconductor Layer 2 First Electrode (Source Electrode)
3 Second electrode (drain electrode)
4 Third electrode (gate electrode)
5 Insulating film

JP-A-5-55568

Appl.Phys.Lett., 69 (26), 4108 (1996) Science, 290, 2123 (2000) Chem. Mater., 19, 2342 (2007)

Claims (10)

An organic semiconductor material represented by the following general formula (I):

(In the general formula (I), R ¹ , R ² , R ³ , R ⁴ , R ⁵ and R ⁶ are each independently a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, or a substituted or unsubstituted group. Represents a substituted alkylthio group or hydrogen, and at least one of R ² , R ³ , R ⁵ and R ⁶ is a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group or a substituted or unsubstituted alkylthio group; And n represents an integer of 1 to 8) In formula (I), the organic semiconductor material according to claim 1, wherein R ² and R ³ are the same. In the general formula (I), R ² and R ³ are identical and, the organic semiconductor material according to claim 1 or 2, characterized in that R ⁵ and R ⁶ are the same. In the general formula (I), R ² , R ³ , R ⁵ and R ⁶ are the same and are selected from one of a methyl group, a methoxy group and a methylthio group, The organic semiconductor material according to claim 1 to 3.   A charge transporting member comprising the organic semiconductor material according to claim 1.   6. An organic thin film transistor comprising an organic semiconductor layer, wherein the organic semiconductor layer comprises the charge transporting member according to claim 5.   A pair of first and second electrodes separated from each other through the organic semiconductor layer and a voltage are applied to flow in the organic semiconductor layer between the first electrode and the second electrode. The organic thin film transistor according to claim 6, further comprising a third electrode having a function of controlling current.   The organic thin film transistor according to claim 7, wherein an insulating film is provided between the third electrode and the organic semiconductor layer.   A display device, wherein a display pixel is driven by the organic thin film transistor according to claim 6.   The display device according to claim 9, wherein the display pixel is selected from a liquid crystal element, an electroluminescence element, an electrochromic element, and an electrophoretic element.

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